Synthetic latex containing a vinyl emulsifying agent and process of preparation



United States Patent Avrom I. Medalia, Newton, Mass.

No Drawing. Application January 14, 1958 Serial No. 708,744

17 Claims. (Cl. 260-29.7)

This invention relates to an improved process for polymerizing polymerizable unsaturated hydrocarbons, and more in particular it relates to the polymerization of vinyl or vinylidene compounds in the presence of a new class of compounds known as vinyl emulsifying agents.

, Heretofore vinyl monomers have been polymerized in the form of an emulsion, that is, the monomers have been dispersed in a liquid, which liquid acts as a dispersing medium, and have been so polymerized that the micelles which are formed in the dispersing medium are the initial locus of the polymerization.

Emulsit'ying agents such as soap have been extensively used in water as a dispersing agent. Suitable initiating agents are added to this emulsion ofthe monomer in water, which results in the formation of polymer particles, which are protected from coagulation by a film of adsorbed emulsifying agent. The suspension of such protected polymer particles is termed a synthetic latex. The emulsifying agent thus functions initially to dissolve the monomer in the micelles formed in the dispersing medium and subsequently to protect the polymer so formed.

Soap, such as potassium laureate and sodium abietate etc. is in no case chemically bound to the polymer but is simply adsorbed on the surface of the'polymer particles and when the resulting latex is coagulated, as for example by adding acids or multi-valent cations, the emulsifying agent contributes nothing to the strength or adhesion of the polymer, but instead may itself or from the decomposition products formed continue to protect the particles from one another in the coagulum. The reaction product of the emulsifying agent with certain coagulating agents migrates within the solid polymer to form aggregates which further weaken the mechanical properties of the When the latex is evaporated as a film, migration of the emulsifying agent to the surface of the film has a deleterious effect upon several properties such as adhesion and resistance to water spotting.

It is an object of the present invention to prepare a latex of improved properties by the process of emulsion polymerization in the presence of an emulsifying agent which is capable of copolymerizing with the monomer or monomers emulsified in the dispersing medium.

It is also an object of the present invention to utilize an emulsifying agent that will be bound to the polymer in such a manner as to prevent migration of the dispersing agent on coagulation and thus avoid the difiiculties encountered in the use of soap as an emulsifying agent.

The vinyl emulsifying agents used herein contain a CH =C group where at least one of the disconnected valences is attached to an electro negative group, which group substantially increases the electrical dissymmetry or polar character of the molecule; such groups as phenyl, chloro, cyano, and vinyl etc. have been found to function in this manner. All of these groups are electron attracting groups. Compounds of this type are disclosed in my copending application Serial No. 389,870, filed November 2, 1953. The potassium salts are prepared by subjecting the methyl ester, such as methyl phenylundecanoate to the following successive steps, acetylation, reduction, dehydration and sapom'fication.

The vinyl emulsifying agents as defined above maybe used to form an emulsion of one or more other monomers in a dispersing medium in which they act as an emulsifying, solubilizing and protective agent and become chemically bound to the polymer, thus avoiding the above-mentioned difliculties encountered with the usual soap emulsifying agent. Examples of such vinyl emulsifying agents are potassium p-styryl undecanoate, sodium p-styryl hexanoate and sodium 14-vinyl-l4-pentadecanoate. Theordinary emulsifying agents such as sodium and potassium soaps of oleic, eleostearic, or undecylenic acid, are not vinyl emulsifying agents in the present sense as these compounds do not contain an electro negative group attached to the vinyl group and therefore do not copolymerize with vinyl monomers under the conditions of emulsion polymerization.

Further examples ofvinyl emulsifying agents are the soaps formed by neutralization of the reaction products of acrylonitrile with either oleic acid or l2-hydroxystearic acid (hydrogenated ricinoleic acid); The reaction between acrylonitrile and oleic acid has been carried out byRoe and Swern (J. Am. Chem. Soc. 75, 5479 (1953));

The reaction between acrylonitrile and l2-hydroxystearic acid has been carried out in a similarmanner. The two products have been identified by acidimetric titration and by infra-red absorption as positional isomers of acrylamidostearic acid. The products of these two reactions have been shown to be different both by infra-red absorption and by virtue of the fact that the product from oleic acid is an uncrystallizable oil, whereas that from 12-hydroxystearic acid is a solid melting at 76.85 C. Although the positional isomerism of these compounds has not been established unequivocally the product from oleic acid will be referred to as l0-acrylamidostearic acid, and to that from l2-hydroxystearic acid as l2-acrylamidostearic acid.

The invention will be more clearly understood from the following examples.

EXAMPLE 1 Ingredients: Parts by Weight Butadiene Water v p-Styryl undecanoic acid 3.18 Potassium hydroxide Equivalent amount Viscosity control agent 0.3 Chain transfer agent 0.4 Initiator 0.1525

The ingredients listed above were agitated together at a temperature of 5 C. At various times samples were withdrawn for test. In the above example:

Viscosity control agent:

Potassium chloride. Chain transfer agents:

Tert-dodecyl mercaptan t 0.1.

Tert-tetradecyl mercaptan 0.1

Tert-hexadexyl mercaptan 0.2 Initiator Redox system:

Di-isopropyl benzene hydroperoxide 0.1

Die thylene triamine 0.05

Ferric iron (as nitrate) 0.0005 Ethylene diamine tetracetic acid 0.002

Patented Jan. 13,

as ez after filtration and washing with ethanol the dissolved soap in the ethanol was titrated with hydrochloric acid, using bromphenol blue as an indicator. Separate experiments showed that no more soap could be extracted from the ethanol coagulated polymer by the conventional ethanol toluene azeotropic extraction procedure, these ex.- periments thus, showed that all the unbound soap entered l s e ll' aa n hi e a e was'q a u ated,

se arate dete mina o of the 9I Q =3 Q f no tassiump-styryl uncleeanoate in the ethanol filtrate was ls m d sre'c rerhe om a y b me r g he nens y of absor a o ultravio i t t a a length h r-afie fic o h St e e P r i f t P-SWIY 9? deeanoie acid. molecule (253. millimicrons).

{Another type of determination was made by dissolving the ethanol coagulated polyrner in chloroform, ren ai ta igs he Par ne W th arm order t move small am ounts" of occluded monomeric potassium p-styryl undecanoate, which would otherwise interfere with the subsequent determination), then re-dissolving the polymer in chloroform, and determining the ultratflet a a qr i Q? t e co-polymerized py y decanoic acid in the polymer, at a wavelength characteristic of the diallgyl substituted bcnzine ring (266 millimicrons) The results of these determinations are given n able L Table I,l)etermination 0f p-styrylundecar pic acid in polybutadier e latex p rs a-pcq- 30 gi e a e n sa d e r r r .l n samrl were, 0 Percent Soap extracted p lymerwrthdraw and analyzed for conversion and extracted T aeatt-Q- i fig ff' soapv (by titration), aceording to the procedures given i metric) p g f above; the results are glven. m Table III. meow i. 35 Table II'.Examples 2-6, all at G. Percent Percent Percent 21 68 42 15 4 40 1 37 Example .s I 2 3 4 5 6 88 .7 0 i i g g g 33 h d. Percent of s ap-c argc 140 l 140 p With mcreasmg conversion the percentage of soap exp-Styryiundgcan ie me n" a. 18 a. 18 6. 36 -n n e jn ethanol decreased, and the percentage of r l itfililifiidiilfiiiifi33h: 1:31;: ::1 f r56 bound in the polymer increases. These results show that ge e i re q eq g q g 915 2. q the potassium p-styrylundecanoate continues to enter the 45 5 Venn 0,219 polymer as polymerization proceeds. t 5

The above results indicate that the polymer formed in the earlier stages of the reaction is a copolymer of buta- Table lrlfArExqmpltes 779 a at 50} C diene and potassium p-styrylundecanoate relat1vely IlCh A t in the latter component. In the earlier stages of the emulsion polymerization the locus of the polymerization 8 9 is the soap micelle, in which the proportion of potassium 70 70 p-styrylundecanoate to butadiene is much higher than in 30 30 the charge as a whole. The copolymer formed in the St hmd an a id 140 mlcelles, designated as copolymer oap, i completely or 55 i0-A1smist$c;ci& "j' .ZIIZIII partially soluble in ethanol depending on the exact cog g r lg gg q' e i 30 polymer composition. The difference between the de- Chain Transit, agentm I q termination of extracted soap by titration and by speci l 0- trophotometryrepresents the amount of copolyrner soap r. t. .W l

Iahle lu Soap, extracted from latices of Examples 2-9 -C? denotes percent conversion "E? denotes percent of soap taken which was extracted in ethanol during coagulation of, the latex, as determined by titration.

Examplez Example3 Example-4 Examples Examplefi Example7 Examples Example?! that is extracted into the ethanol, since this copolymer soap exhibits a titration behavior similar to that of the monomeric potassium p-styrylundecanoatc, but does not exhibit an absorption maximum at 253 millimicrons. As the conversion increases the difierences between the results of these two determinations becomes smaller, indicating. reater coprecipitation of the copolymer soap with the poly-butadiene, both mechanically and beeause of the cross linking between the initially formed copolymer soap and the subsequently formed poly-butadiene.

In the re-precipitation of the polymer prior to the spectrophotometric determination of the bound soap in the polymer, about half of the polymer is lost (i. e. is soluble in the ethanol-chloroform solution). This lost polymer includes all the copolymer soap which is not extracted into the, ethanol during the coagulation step. The. spectrophotometrically determined value of soap copolymerized' (column 4 of Table I) therefore represents the percentage. ofpotassium p-styrylundecanoate which enters thev butacliene rich copolymer formed during the laterstages. of conversion. The sum of the values in the third and fourth columns of Table I is 56%i l% at all three conversions; the remainder of the soap, namely 44%., must represent the percentage of soap which en'- tered into the copolymer soap, in the initial stages of the reaction.

EXAMPLES 2-9- Ingredients were charged into pressure vessels accord: ing to the torrnula of Table II. These ingredients were perperpe rperperperper perper: perperper: perper.- 'per pen. cent cent cent cent; cent cent eent cent cent cent cent; cent cent cent 31 61 40 75 3 82,. 30 104 34 100 60 42 90 70 77 and copolymer soap. Therefore, the difference between 100% and this value E represents the lower limit to be set on the percent of soap chemically bound in the copolymer, whereby the termcopolymer denotes all polymer formed in the reaction, of whatever ratio of vinyl emulsifying agent to vinyl monomer.

Examples 1 and 2 show comparable results in'poly-" butadiene latices prepared with different amounts of mercaptan. Example 3 shows the incorporation ofpotassium p-styrylundecanoate into a ,butadiene-styrene copolymer. Example-4 shows that with double the usual amount of potassium p styrylundecanoate, the percentage of soap incorporated into the polymer remains unchanged. Example 5 shows the incorporation of a different vinyl emulsifying agent, potassium IO-acrylamidostearate, into a butadiene styrene copolymer. Examples 7 to 9 give the results of polymerizations carried out at different temperature and with a different initiating system than in the previous examples. Examples 7,8 and 9 show the use of three different vinyl emulsifying agents in butadiene and butadiene-styrene emulsion polymerization. In Examples '7-9 potassium peroxydisulfate was used as an initiator. v

EXAMPLE 10 As examples of the coagulation of vinyl emulsifying agent latices, the latices, of Examples 1 to 9 have been coagulated by pouring dropwise into ethanol thus producing a fine crumblJn this crumb the polymer'contains bound vinyl emulsifying agent, as the potassium soap. These latices have also been coagulated with acidified isopropanol, also forming a fine crumb. In this process the vinylemulsifying agent is transformed to the acid state, so that the copolymer contains bound long-chain acid molecules rather than boundsoap molecules.

These latices have also been coagulated with calcium nitrate by the coagulant dip process. .Flms of 10 to mil thickness were formed. In these films and in the dried polymer obtained thereof the bound vinyl emulsifying agent had been transformed to the calcium salt.

As further examples of the preparation of solid polymer from latex, the latex of Example 6 was coagulated by dropwise addition'of 0.5 'N hydrochloric acid to the latex at total solids concentration.- Another portion of this latex was coagulated by the addition of 10% sodium chloride. Another portion of this latex was coagulated by the addition of aluminum ammonium sulfate. I

PROPERTIES- OF LATEX PREPARED WITHW'INYL EMULSIFYING AGENTS Example 3 represents a typical butadiene-styrene latex showing the advantageous properties obtainable by the use of a vinyl emulsifying agent. A portion of this latex was withdrawn at 81% conversion, shortstopped with potassium dimethyldithiocarbamate, vented to remove butadiene, and steam distilled to strip off the styrene. The total solids concentration was adjusted to 40.8%. The pH of the latex was 10.3; the turbidity (standard RFC method) was 0.172; and the surface tension was 71.8 dynes/cm. The first two properties are in the range normally found for a latex prepared under similar conditions with an ordinary soap such as potassium oleate; however, the surface tension is unusually high as compared with an oleate latex. This high surface tension is indicative of the very low monomeric soap content of the, latex, and is typical of latices prepared with vinyl emulsifying agents under such conditions that a major portion of the vinyl emulsifying agent has entered the copolymer. The latex had the useful property of being pressure-sensitive. Latices so prepared may be concentrated by usual methods such as evaporation or creaming.

A unique property of the vinyl emulsifying agent The blocking" was not laticesas compared with ordinary synthetic latices, is

the cohesiveness of'the dried film. The latex prepared mental in the application in which cohesiveness-is desirable, such as'in self-sealing envelopes, shirt bands, etc.

exhibited by the latex in Example3.

Another unique property of the vinyl-soap latices is the resistance of the dried film to water spotting. This resistance develops immediately upon air drying in contrast to a latex prepared with a volatile base soap such as an amine or ammonium fatty acid soap, which develops resistance'to water spotting only upon heat treatment s'ufl'lcient-to decompose the soap. Latices prepared With sodium orpotassium soap of the ordinary type do not develop resistance 'to water spotting even by heating. Vinyl soap latices especially those made at high conversion show excellent retention of strength in saturated paperswhen suchsaturated paper is tested for tensile properties while wet.- In one example a 100% conversion product containing 3.18% of vinyl soap in the monomer charge shows .a wet tensile strength of of the dry value in such a test. The latex made with a similar v paper therefore, indicates the'application of these products in conditions where exposure to moisture would be common.

Good cohesiveness is also exhibited by the latices of 7 several of the other examples given above, such as Nos.

5, 6 and 9, at 75%, 100% and conversion, respectively. Latices Nos- 5 and 6 exhibit good resistance to water spotting." The essential importance of the present invention is that useful properties, such as cohesiveness and resistanceflto water spotting, are obtained in a suitably balanced polymerization formula using a vinyl emulsifying agentawhereas with a conventional emulsifying agent, comparable formulae do not give these useful properties, and indeed no formula has as yet been found in the art which will yield these tional emulsifying agent.

It is of course understood that the application of vinyl emulsifying agents is not limited to the examples given, either with regard to the'particula'r vinyl emulsifying agents employed, or the monomers, or other ingredients ofthe formula, or conditions of polymerization. The invention lies in the use of any vinyl emulsifying agent, defined as above, in=the emulsion polymerization of any vinylor vinylidene monomer. The useful properties of latex and polymer prepared in the'manner of this invention are also not limited to those described above, but other unique properties are also inherent in these latices and polymers by virtue of their unique character.

The latices produced by vinyl emulsifying agents may be coagulated and washed by methods well known in the art, including salt and acid coagulation. Such products, as is customary may require antioxidant additives before coagulation, washing and drying. By variation of kind and amount of modifier, the viscosity of the dry polymer can be controlled to allow ready processibility in rubber milling equipment. These products may also be varied as regards conversion and gel content, and may be stripped, prior to coagulation, in standard manners.

A 'vinyl emulsifying agent is in itself polymerizable. This invention shows that when used as an emulsifying agent in a monomer system to be emulsion polymerized, this vinyl emulsifying agent is capable of resulting in a normal polymerization of the monomer system and main tains stability during the reaction, as shown by absence of ties or coagulum. In addition, the vinyl emulsifying agent itself becomes ghemically bonded to the main polymer properties with a conven- '2' and gives new and improved properties to the latex polythat or its coagulated product.

As will be evident to those skilled in the art, various modifications of this invention can be made or followed in the light of the foregoing disclosure or discussion without departing from the spirit or-scope of the disclosure or from the scope of the claims;

What is claimed is:

l. A synthetic latex comprising a colloidal aqueous suspension of a copolymer of 1,3-butadiene, styrene and a vinyl emulsifying agent, comprising a water soluble soap of an acid selected from the group consisting of psty'rylundecanoic acid, IO-aerylamidostearic acid, p-acrylylphenylundecanoic acid, IO-acryloxystearic acid and 1 2- acryloxystearic acid.

2. A synthetic latex comprising a colloidal aqueous suspension of a copolymer of at least two vinyl monomers, at least one of said monomers being .a vinyl emulsifying agent, comprising a water soluble soap of an acid selected from the group consisting of p-styrylundecanoic acid, acrylamidostearic acid, p-'acrylylphenylundecanoic acid, lO-acryloxystearic acid and -12-acryloxystearic acid and at least one of said monomers being a monomer other than said vinyl emulsifying agent.

3. A synthetic latex comprising a colloidal aqueous suspension of a polymer of vinyl monomerscharacteri zed by a vinyl emulsifying agent comprising a water soluble soap of an acid selected from the group consisting of pstyrylundecanoic acid, IO-acrylamidostearic acid,,p-acryl ylphenylundecanoic acid, IO-aeryloxystearic acid and 12- acryloxystearic acid being chemically bound to thetpolymer. Y

4. A synthetic latex comprising a colloidal aqueous suspension of a copolymer of 1,3-butadiene, styrene'and a.

vinyl emulsifying agent comprising a water soluble soap of an acid selected from the group consisting "of pstyrylundecanoic acid, 10-acrylamidostearic acid, 11- acrylylphenylundecanoic acid, IO-acryloxystearic acid and 12-acryloxystearic acid characterized by the vinyl emulsifying agent being chemically bound by the'polymer.

5. A synthetic latex comprising a colloidal aqueous suspension of a polymer of vinyl monomers in which the colloidal stabilizing agent is the water soluble soap of p styrylundecanoic acid, partially vin a monomeric and partially in a polymerized form.

6. A synthetic latex comprising a colloidal aqueous suspension of a polymer of vinyl monomers in which the colloidal stabilizing agent is the water soluble soap of pstyrylundecanoic acid, a portion of which is chemically bound to a'polymer.

7. A synthetic latex comprising a colloidal aqueous suspension of a polymer of vinyl monomers in which the colloidal stabilizing agent is the water soluble soap of IO-acrylamidostearic acid, a portion of which is chemically bound to a polymer.

Q 7 c: 8. A synthetic latex' comprising a colloidal aqueous suspension of a polymer of vinyl monomers in which the colloidal stabilizing agent is the water soluble soap or p:acrylylphenylundecanoic acid, .a portion of which, is

aqueous emulsion of 1,3-butadiene, styrene and a water chemically bound to a polymer.

'9. A synthetic latexcomprising a colloidal aqueous suspension of a'polymer of vinyl monomers in which the colloidal stabilizing agent is the water soluble salt of 10- acryloxystearic acid, a portion of which is chemically bound to a polymer.

10. A synthetic latex comprising a colloidal aqueous suspension of a polymer of vinyl monomers in which the colloidal stabilizing agent is the water soluble soap of 12- acrylamidostearic acid, a portion of which is chemically bound to the polymer.

11. The process of subjecting to polymerization vinyl monomers in a dispersing medium with a vinyl emulsifying agent comprising a water soluble soapof an acid selected from the group consisting of p-styrylundecanoic acid, IO-acrylamidostearic acid, p-acrylylphenylundecanoic acid, 10'acryloxystearic acid and lZ-acryloxystearic acid.

12. The process of subjecting to polymerization in an aqueous suspension vinyl monomers with a vinyl emulsifying agent comprising a water soluble soap of an acid selected from the group consisting of p-styrylundecanoic acid, IO-acrylamidostearic acid, p-acrylylphenylundecanoic acid, IO-acryloxystearic acid and IZ-acryloxystearic acid.

13. The process 'of subjecting to polymerization an aqueous emulsion of 1,3-butadiene, styrene and a vinyl emulsifying agent comprising a water soluble soap of an acid selected from the group consisting of p-styrylundecanoic acid, IO-acrylamidostearic acid, p-acrylylphenylundeca'noic acid, IO-acryloxystearic acid and 12-acryloxystearic acid.

14. The process of subjecting to polymerization an soluble soap of 10-acrylamidostearic acid.

15. The process of subjecting to polymerization an aqueous emulsion of 1,3-butadiene, styrene and a water soluble soap of p-styrylundecanoic acid.

16. The process of mixing vinyl monomers together with a dispersing medium and a vinyl emulsifying agent comprising a water solublesoap of an acid selected from the group consisting of p-styrylundecanoic acid, lO-acrylamidostearic acid, p-acrylylphenylundecanoic acid, 10- acryloxystearic acid and l'2-acryloxystearic acid, and sub jecting this mixture to polymerizing conditions whereby copolymerization of the vinyl monomers together with the said vinyl emulsifying agent takes place.

17. The process as described in claim 16, wherein said vinyl monomers are styrene and 1,3-butadiene.

No references cited; 

1. A SYNTHETIC LATEX COMPRISING A COLOIDAL AQUEOUS SUSPENSION OF A COPOLYMER OF 1,3-BUTADIENE, STYRENE AND A VINYL EMULSIFYING AGENT, COMPRISING A WATER SOLUBLE SOAP OF AN ACID SELECTED FROM THE GROUP CONSISTING OF PSTYRYLUNDECANOIC ACID, 10-ACRYLAMIDOSTEARIC ACID, P-ACRYLYLPHENYLUNDECANOIC ACID, 10-ACRYLOXYSTEARIC ACID AND 12ACRYLOXYSTEARIC ACID. 